Friends:

Imperturbable is one not Opposing any Pain!

The Blessed Buddha once said to some deadly sick bhikkhus:
Any Bhikkhu should await his time aware and clearly comprehending...
This is our instruction to you! While a bhikkhu lives in this way, aware and
clearly comprehending, enthusiastic, keen, and determined, if there arises
in him a painful feeling, then he understands this: "There has arisen in me
this painful feeling. Now that is dependent, not independent! Dependent on
what? Dependent on just this contact! But this contact is impermanent,
conditioned, and dependently arisen... So when a painful feeling has arisen
in dependence on a contact that is impermanent, conditioned, & dependently
arisen, how could it ever then itself be permanent?" He dwells in this way
always contemplating the impermanence of any contact and the transience
of any painful feeling, and he considers thus the inevitable vanishing, fading
away, ceasing, & the therefore necessary relinquishment of all conditioned
constructions! In this very way is his latent tendency to aversion towards
any painful contact & instinctive repulsion of any painful feeling gradually
eliminated. He therefore then understands: With the breakup of this body,
at the exhaustion of this fragile life, any feeling, all that is felt, neither
being opposed, nor clung to, will cool down right there...

More on systematic relinquishment:
https://What-Buddha-Said.net/drops/Free_from_Fear.htm
https://What-Buddha-Said.net/drops/II/Leaving_All_Behind.htm